Packard Forum Index » Modification Discussion

Hi Jack

Well, when you know a subject as well as you do Packard V8 engines, someone needs to say so. Few of us have the depth of experience and knowledge you have. Therefore we need to take seriously your advice when it comes to rebuilds and/or modifications.

The V8 bearing failures were likely rooted in the inadequate time to design and test the engine, given the mandate to have a new V8 ready for '55 production. When I read about the 25,000 mile endurance run made in '54 as proof of the engine's durability, I wonder why those trials didn't take place in 1952 or 1953.

I continually wonder what the engine engineering department was working on after the introduction of the '49 Olds and Cadillac short-stroke, OHV V8 engines. If they were still trying to prefect the straight eights, they were just tilting at windmills. Once a new type of engine design proves itself to the consumer to have major benefits, trying to convince them to hold onto the old technology is just pointless.
Packard should have had a fully prefected V8 engine ready for production easily before '55 rolled around. As a maker, Packard wasn't always first but when they did field a new design, it was pretty thoroughly prefected.

Steve

Quote:
"FWIW, the Chevy V8s never had main bearing or crankshaft problems until they went to overdrive automatics and lockup torque converters. This increased engine loading at lower RPMs caused heretofore unseen wear."

Which begs the question:
What did Chevy do to correct the problem????? Maybe the same correction nneeds to be made to the Packard V8 models.

I drove several old powerglides up thru mid 1970's models. 6's and 8's. They routinely shifted to high at about 15 mph. They'd run 150k Miles with no excessive centre bearing wear other than normal wear expected at 150K miles.

Quote:

Not the same thing at all. There is a night-and-day difference because the Powerglide does not have a lockup converter as did the TwinUltramatic and the later GM 4-speed autos. The Powerglide converter is a very loose connection between the engine and the rear wheels. With a locked converter, the engine cannot increase road speed without a commensurate increase in the direct load on the bearings. With an open converter, there is no direct connection. The slippage decreases fuel economy, increases transmission fluid temperature, but seems to save the engine main bearings.

jack vines

ok. but it still begs the question as to what did chevy do to prevent (or fix) main bearing wear when the lockup converter/OD transmssions went into production??? I have no idea. Maybe the same fix, whatever it is, needs to be applied to the Packard V8 / TwinUltra.

I don't understand this. Standard shift cars don't generally have a reputation for eating main bearings, and in high or OD they're no different in that respect than an Ultramatic or other automatic with a locked converter. IF that was a cause of Packard's bearing wear (a BIG IF), it might be attributed to lockup occuring at such low road speeds, like 22 rpm. I would probably have my 34 Eight in 3rd gear by then, but it has 4.69 gears. With a more "normal" rear axle ratio and standard shift, I suspect you are rarely in high gear at 22 mph as you accelerate.

My own opinion is that a good driving habit with Ultramatics is to use the throttle when possible to delay the lockup to 30 mph or so. Or have the governor reworked to accomplish the same thing. I try very consciously to avoid lugging, for example up a hill, at low road speeds in lockup. Just tick the throttle and kick back into converter when you're at such low road speeds to avoid lugging.

I doubt modern automatics lockup at road speeds in the 20s. At least none that I ever drove.

OWen, My experiences are the same as yours.

Had the center main bearing cap removed from my 56 Executive about 9 months ago. At 0.002" clearence plastigauge (yes crank jacked up) showed no unusual wear in the cap shell. I didn't check the other mains. .002" should be somewhere near high end of acceptable clearence for service. Engine has 55K miles on it.

I routinely lug every engine i've ever owned at low speeds. Especialy the Packard. It's just not a dragster.